Help!!!
 

Running:
Macbook Pro 15" Intel Core2 Duo 2.2GHz
4 GB 667 MHz DDR2 SDRAM
Leopard OS X 10.5.4

I don't know what in the world is going on, but starting about a week ago, my Mac started exhibiting very bad problems:

-Programs would freeze for minutes at a time, most of the time ending up crashing completely
-Firefox loads web pages at about 3 kb/s download speed, most of the time just timing out
-Almost all programs load abysmally slow
-Using Dashboard or Spaces makes the OS crash, requiring a restart
-The whole OS seems unstable

Needless to say, the alarm bells stated going off when I found myself saying "If only Leopard would be as stable as Vista" as I used bootcamp to switch to Vista.

I've used PC's with Windows for years so I know what it looks like when a computer is infected with a virus, and Leopard doing this makes me very concerned that there may be some sort of virus dwelling in the system. Yes, I said it, horrible as that may sound, that's how it seems. I hope to god that I am wrong and just have something trivial going on.

If that is the case, Someone please tell me how to fix this! I'm desperate for a solution!

(Programs that crashed while trying to post this message)
-Firefox (4 times just trying to get into this forum)
-Safari (3 times, tried using as an alternative to Firefox to get to the forums)
-MSN messenger (2 times)
-iTunes (2 times)
-System Preferences (Didn't know it could crash, but it is still sitting there bouncing up and down like it is trying to load)
-Mail (2 times)

HELP!!!! *begs*

I doubt that it's a virus. So let's leave that for last.....

Do you have a copy of OnyX on hand? If not, download a copy from here:

http://www.macupdate.com/info.php/id/11582 (It's free)

Install it and run the program. Let it go through all the routines especially repairing permissions. If that doesn't help, boot the machine with your Leopard disk, run first aid and verify the disk.

Last, so you'll feel better... download this free Mac AV scanner and run it.

http://mac.softpedia.com/get/Antivirus/ClamXav.shtml

Regards.

Mkay ran the scan, thankfully no viruses. Also, I ran OnyX and it found that my startup volume was invalid so I repaired that, and at the same time went into my disk utility and repaired the permissions. However, it's still acting the same way.... It's still being very unstable and I just switched back over to Vista to post this because Firefox wouldn't even open...

Okay now I can't even boot into the OS, it just sits there with only my wallpaper loaded and has the spinning wheel of doom while it tries to load the dock >.< I think I may just need to wipe the system and redo it because I can't figure out what else to do and I'm getting tired of Vista

As a last cry for help before I wipe and redo my system, anyone have any ideas?

Did you upgrade the ram a week ago?
Did you run software update prior to that instability

Otherwise, yes, back up your files and go for a fresh install, also consider reformating first to eliminate any bad format issues

You'll have to back up that claim with any evidence there is a virus out there. The only Trojans I know of typically just redirect your DNS servers, not have the ability to hack the core system and introduce instability

My RAM upgrade was months and months ago and my system worked fine after those. This problem is very recent. And also no new software, so I think I'm just going to have to wipe